Reduction of sulfur activity of sulfurized alkyl phenols

ABSTRACT

THE SULFUR ACTIVITY OF SULFURIZED ALKYL PHENOL LUBRICATING OIL ADDITIVES TOWARDS SILVER IS REDUCED WITHOUT REDUCTION IN THE ACTIVITY OF THE ADDITIVE BY TREATMENT OF THE SULFURIZED ALKYL PHENOL LUBRICATING OIL ADDITIVE WITH A TERVALENT PHOSPHOROUS COMPOUND.

United States Patent US. Cl. 260-137 2 Claims ABSTRACT OF THE DISCLOSURE The sulfur activity of sulfurized alkyl phenol lubricating oil additives towards silver is reduced without reduction in the activity of the additive by treatment of the sulfurized alkyl phenol lubricating oil additive with a tervalent phosphorous compound.

BACKGROUND OF THE INVENTION Field of the invention Sulfur-containing lubricating oil additives are limited in their use in railroad diesel engine lubricating oils. Because of the prevalent use of silver bearings in railroad diesel engines, sulfur-containing lubricating oil additives which lead to silver corrosion must be avoided.

Sulfurized alkylphenols find wide use in lubricating oil additives. The sulfurized alkylphenols can be used as antioxidants. Furthermore, the sulfurized alkylphenols are frequently used as detergents and for acid neutralization, either as an alkaline earth metal phenates or the overbased alkaline earth metal phenates. Since railroad diesel fuels frequently contain significant amounts of sulfur, the alkylphenates serve to neutralize any of the sulfur derived mineral acids which might otherwise accumulate in the lubricating oil.

Description of the prior art Sulfurized alkylphenates have appeared in numerous patents. See, for example, US. Pat. Nos. 2,409,687; 2,680,- 096; 3,178,368, and 3,367,867, as well as the patents referred to therein. In many instances, the sulfurized alkylphenols or sulfurized alkylphenates have either not been used in railroad diesel oils or means have been found for reducing their sulfur activity.

SUMMARY OF THE INVENTION Sulfurized alkylphenols or their alkaline earth metal salts having reduced silver corrosion tendency are obtained by treating the sulfurized alkylphenol or its alkaline earth metal salt with a tervalent organic phosphorous compound and removing the resulting sulfur-containing phosphorous compound.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sulfurized alkylphenol or its alkaline earth metal salt is contacted with the tervalent phosphorous compound at elevated temperatures for a sufiicient time for reaction and unreacted phosphorous compound and optionally the resulting phosphorothioate compound removed. The amount of the tervalent phosphorous compound will generally be from about 0.1 to 10 weight percent based on the sulfurized alkylphenol, more usually from about 0.5 to 7 weight percent.

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The tervalent phosphorous compound may be added batchwise or incrementally to the sulfurized alkylphenol. Preferably, the tervalent phosphorous compound is added incrementally. Depending on the amounts of the materials, and the particular reactant used, the addition may require from about 15 minutes to about 6 hours. The total time of contact between the tervalent phosphorous compound and the sulfurized alkylphenol may vary from about 15 minutes to 24 hours, more usually 0.5 hour to 12 hours.

The temperature forthe reaction will be at least C. and more usually from about to 200 0, preferably from about 100 to C.

The reaction may be carried out either neat or in an inert medium usually a hydrocarbon medium. The hydrocarbon may be aliphatic or aromatic or combinations thereof. It is frequently useful to employ an oil of lubricating viscosity as the reaction medium, for once the phosphorous compounds are removed, the product is ready to be used directly.

The amount of tervalent phosphorous compound employed will depend on the degree of sulfur reduction desired. This will usually be determined by the effect of sulfur reduction on the properties of the sulfurized alkylphenol. Once the amount of sulfur reduction desired has been determined, the amount to be employed of tervalent phosphorous compound is set. Usually, the amount of sulfur reduction will vary from about 3 to 20 weight percent, based on the original amount of sulfur, more usually from about 5 to 12 weight percent.

Reactants The tervalent phosphorous compound will usually be a tri(lower alkyl) phosphite, more usually trimethyl phosphite. To the extent that trimethyl phosphite has the highest percentage of phosphorous and is the most inexpensive, it is preferred. Furthermore, because it has a relatively low boiling point, the trimethyl phosphite can be easily removed from the reaction mixture. While other trialkyl phosphites may be used or even other tervalent phosphorous compounds, for the above reasons, trimethyl phosphite is the preferred reactant.

The sulfurized alkylphenols will, for the most part, have the following formula:

wherein m is O to 2; n is generally of from 1 to 3, averaging at about 1.5 to 2.5; M is hydrogen, alkaline earth metal (calcium or barium), and when alkaline earth metal,

the second valence may be satisfied by phenoxide, alkoxide or hydroxide; and R is an aliphatic hydrocarbon group of from 8 to 30 carbon atoms.

For the most part, the alkylphenol compositions will have in equal to 0. For these compositions the formula will be as follows:

wherein M and R are as defined previously, and I1 is in the range of 1 to 3, averaging at about 1.5 to 2.

The sulfurized alkylphenols may be prepared by a variety of methods. Directly, alkylphenols can be reacted with sulfur monochloride in the presence of a catalyst. Alternatively, the alkylphenols may be sulfurized by reaction with sulfur in the presence of a basic catalyst. Other methods may be used as desired.

The sulfurized alkylphenols will generally have from about 5 to 20 weight percent sulfur, more usually of from about 7 to weight percent sulfur.

The sulfurized alkylphenols when present as the alkaline earth metal salts may have stoichiometric equivalents of metal or phenol or may have enhanced amounts of the basic metal, either as its hydroxide, alkoxide or carbonate, dispersed in a hydrocarbon medium.

As already indicated, oils may be used as an inert reaction medium. The lubricating oils include such petroleum derived oils as parafiin base, naphthenic base, asphaltic base and mixed base lubricating oils. Other lubrieants include lubricants derived from coal products and synthetic hydrocarbons such as alkylated aromatics or alkylene polymers. The lubricating oils generally have viscosities of from about 35 to 50,000 Saybolt Universal seconds (SUS) at 100 F.

EXAMPLES The following examples are offered by way of illustration and not by way of limitation.

EXAMPLE I Into a reaction vessel was introduced 1,100 g. of 2,2- bis(4-polypropylene phenol) disulfide (polypropylene of an average of about 12 carbon atoms) at 75 weight percent solution in oil and the solution heated to 150 C. To this solution was added incrementally 42 ml. of trimethyl phosphite with stirring. The mixture was then stirred overnight at 150 C. Residual trimethyl phosphite was removed by diluting the reaction mixture with 1,500 ml. of xylene and distilling off the xylene. The product was then airblown at 90 C. for 2 days. While the original product had 7.0 weight percent sulfur, the final product had 5.96 weight percent sulfur; 0.7 weight percent phosphorous and a molecular weight of 438.

EXAMPLE II Into a reaction vessel was introduced 1,100 g. of sulfurized calcium polypropylenephenoxide (polypropylene of an average of about 12 carbon atoms; phenol to calcium ratio of 1.121, as a 40.5 weight percent solution in oil and 94 ml. of trimethyl phosphite added slowly over a period of about /2 hr. while maintaining a temperature of 150 C. At the end of the addition, 1,500 ml. of xylene was added and the solution stripped of xylene and trimethyl thiophosphate. The product anlyzed at 3.2 weight percent sulfur.

EXAMPLE III A sulfurized calcium polypropylenephenoxide (1,100 g.) substantially the same as in Example II, but having 9.25 weight percent calcium, primarily as calcium carbonate, was introduced into a reaction vessel and heated to 150 C. To the oil solution was added slowly over a period of about 0.5 hr. 114 ml. of trimethyl phosphite while maintaining a temperature of 150 C. At the end of this time, 1,500 ml. of xylene was added and the solution stripped of xylene and trimethyl thiophosphate. The final product had 3.39 weight percent sulfur.

In order to determine the effect on silver corrosion of treating the various additives with trialkyl phosphite, the following test was carried out. In the test, a silver test piece is used made of pure silver, 99.9 percent fine, soldered to a backing of soft steel. Both silver and baclv ing are nominally /s in thickness, 1.3 inches OD. and 1.0 inch LD. The silver surface is grooved by 3 equally 4: spaced slots, 0.05 inch deep, obtained by /4 end mill chamfered 30 on its lower end.

The silver test piece is annealed after machining and after each use to remove any Work hardening in the silver. The annealing is carried out at 650 F. for /2 hour, allowing to slowly cool to room temperature. Following annealing, both sides are surface lapped to obtain a smooth flat surface of approximately 9-12 microinches finish.

The steel test specimen is made to duplicate the metallurgy of the wrist pin steel in the EMD locomotive engine. The material is AISI Steel No. 8620H. Heat treatment to a minimum hardness of 58 Rockwell C is achieved by carburizing for 0.04-0.05 finish case depth, pit cool; reheating to 1,475 F. and oil quenching; followed by tempering at 400 F. for 8 hours. Both sides are finishedlapped to a finish of 35 microinches. Nominal dimensions are 1 /2 inches OD, 0.9 inch ID, and 0.2 inch thick.

A motor-driven mechanism is used to obtain oscillatory motion at the test surfaces. A small quantity of the lubricant to be evaluated is placed in the oil cup and the machine assembled. A calibrated spring applies a 510 pound load on the bearing surfaces. An electric heater is provided in the base of the apparatus to maintain the oil at a temperature of 350 F.

The apparatus is assembled and the temperature slowly raised to 350 F. During this time, the washers are maintained in an oscillatory motion. When the temperature of 350 F. is attained, the test is carried out for a further 20 minutes. In effect, the run consists of a 10-minute breakin, a 30-minute heatup at 350 F. and then 20 minutes at constant temperature operation.

The results are reported as wattage and in a few instances as silver loss. Wattage is proportional to the frietion between the steel and silver washers, lower wattage indicating lower friction. Silver loss is an indication of corrosion and wear of the silver washer. The following table indicates the results obtained:

TABLE I Example Ag. loss, mg. Watts, 45/00 min.

[I3 3 230/232 "IA 147/143 {B 3 8 234/232 11% g (1) 11104174 2 2 210 "in 0 d 150/149 1 Results reported at 45 and 60 minutes.

2 Formulated in 480 neutral oil as 2.0 weight percent of Ex. I and 3.5 weight percent of a commercial polyisobutenyl SuCCllllllIidG 0t tetra ethylene pentamine.

3 B=betore treatment with phosphite; A=alter treatment with pliosphite.

4 A formulation containing 2 weight percent of the material of the example indicated, 2 weight percent; of a commercial amino nitrogen containing ashless lubricating oil detergent, 6 mM. of a commercial calcium sulfonate, 50 mM. of a commercial calcium alkylphenate, 0.3 weight percent of a paratlin polysulfide and 0.025 weight percent of u corrosion inhibitor.

5 6 wherein m is 0 to 2; n is in the range of 1 to 3, averaging References Cited over the entire composition in the range of 1.5 to 2.5; walling et 31 Am Chem Soc, vol 79 (1957),

M is hydrogen or alkaline earth metal; and R is an alkyl p 5326, QD1A5 group of from 8 to 30 carbon atoms, with tri(lower alkyl) phosphite in an amount sufficient to reduce the 5 CHARLES B. PARKER, Primary Examiner initial sulfur content by from 3 to 20 weight percent. A SUI-TO Assistant Examiner 2. A composition according to claim 1 wherein said trialkyl phosphite is trimethyl phosphite, said temperature US. Cl. X.R.

is in the range of 100 to 200 C. and m is 0. 252--45; 260-985 

